Electric heating apparatus



y 1939- E. N, CALHOUN 2,158,604

ELECTRIC HEAT ING APPARATUS Original Filed April 15, 1957 I I Ernast N.C'a1'houn i 2 INVENTOR BY MMM flW ATTORNEYS Patented May 16, 1939 UNITED STATES PATENT OFFICE mesne assignments, Pittsburgh, Pa.

to Edwin L. Wiegand,

Original application April 13, 1937, Serial No. 136,588. Divided and this-application January 6, 1938, Serial No. 183,605

15 Claims.

My invention relates to electric heating apparatus, and more particularly to such apparatus of the forced convection or circulation type, and the principal object of my invention is to provide new and improved apparatus of these types. This application is a division of my application Serial Number 136,588, filed April 13, 1937.

In the drawing accompanying this specification, and forming a part of the application, I have shown, for purposes of illustration, one form which my invention may assume. In this draw- Figure 1 is a front elevation of heating apparatus embodying my invention,

Figure 2 is a section, partly in elevation, taken along the line 2-2 of Figure 1, looking in the direction of the arrows, and

Figure 3 is an electrical diagram of one way, in accordance with my invention, in which the heating units in the illustrated heating apparatus may be connected.

Referring to Figures 1 and 2, the heating apparatus here shown comprises two heating units III, II, the' planes of which are oifset axially, and two heating units 12, I3, spaced axially from the units I0, I I, and the planes of which are similarly offset axially. The heating units III, II, I2, I3 may be of any suitable form. They are here shown as of the type comprising a metallic sheath containing a resistor embedded in re fractory insulating material, and the sheath carrying a plurality. of finned collars. Specifically, if desired, the heating units may be of the form shown in my hereinbefore mentioned application. Air is adapted to be blown against the units I2, I3, and III, II by a fan I4 driven by a motor I5. The motor I5 is here shown as disposed within an arcuate nearly cylindrical bracket I6 and this bracket also serves to support the heating units I0, II, I2, I3. The stator of the motor I5 is fastened to the arcuate bracket I6 by means of screws I1.

Extending in a generally radial direction from the arcuate bracket I6 are three supporting plates I8, I9, 20, one of which I9 is visible in side elevation in Figure 2. The radially outermost portion of each supporting plate I8, I9, 20 extends rearwardly diagonally outwardly and the front side of each plate is provided with, in this instance, two open end slots 2I for receiving the general body portions of the heating units III, II,'and, similarly, the rear margin of each supporting plate is provided with two open end slots 22 for receiving the general body portions of the units I2, I3, so that the four units are disposed as shown in Figure 2. If desired, the unitsmay be brazed or otherwise fastened to the supporting plates I8, I9, 20. The. arcuate bracket I6 may have integral therewith legs 23, 24, or may be supported in other suitable ways, several of which are shown in my aforesaid copending application, and the lower ends of the heating units III, II, I2, I3 may, if desired, be fastened -to these legs as described in said copending application or may be fastened in any other suitable manner.

The heating apparatus shown in Figures 1 and 2 is here shown as provided with a housing 25,- and this housing may be provided at its rear end with any desired form of reticulated fan guard 26. In this instance switches 2! for controlling the heating units I0, II, I2, I3 are shown as mounted on the lower portion of the housing 25.

If desired or necessary a deflecting means 28 may be provided for preventing the air from passing between the arcuate bracket I6 and the inner peripheries of. the heating units I0, I2, without contacting these units, by providing, in this instance, a deflecting plate or bafile 28 of frustro-conical form disposed around and fastened to the bracket 16.

Where, as in the illustrated embodiment, four heating units III, II, I2, I3 are provided and it is desired that these units be connectable to a three phase alternating current system to constitute a balanced load thereon, the two outer units I I, I3 may be each made so that when connected across a phase of a three phase system, at full voltage, these units will operate at their full capacity; on the other hand, the units I0, I2 may be so made that when each is connected across a phase of a three phase system, at full voltage, each unit willoperate at a capacity, one-half that of the outer and longer units it; I3. In such case connection may be made to the conductors of the three phase system 29,30, 3!, as diagrammatically shown in Figure 3, the unit II being connected across the phase 29, 30, and the unit I3 being connected across the phase 30, 3I and the two units I0, I2 being connected in parallel across the phase 29, 3I. It will be evident that the same conception may be employed in embodiments of heating apparatus having other numbers of units not divisible by the number of phases of a supply circuit.

From the foregoing it will be apparent to those skilled in the art that the illustrated embodiment of my invention provides a. new and improved electric heating apparatus, and accordingly, accomplishes the principal object of my invention. 0n the other hand, it also will be obvious to those skilled in the art that the illustrated embodiment of my invention may be variously changed and modified, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of my invention, or sacrificing all of the advantages thereof, and that accordingly, the disclosure herein is illustrative only, and my invention is not limited thereto.

I claim:

l.'In combination: a plurality of electrical heating elements for connection to a multi-phase' supply, the number of said heating elements being greater than the number of phases of the supply and being other than a multiple of said number of phases, at least two of said heating elements each having a capacity a predetermined fraction of the individual capacity of the other elements; and means for so connecting said elements to the supply that the load on the supply is balanced.

2. In combination: a plurality of electrical heating elements in number other than a multiple of three constructed and arranged for connection to a three phase source of supply to provide a balanced load on said supply, at least two of said elements each having approximately onehalf the capacity of the other elements.

3. In combination: a plurality of arcuate electrical heating elements in number other than a multiple of three constructed and arranged for connection to a three phase source of supply to provide a balanced load on said supply, a first pair of said heating elements defining circles of substantially equal diameter the elements of the pair being disposed coaxial, a second pair of said heating elements defining circles of substantially equal diameter but of a diameter substantially smaller than that of said first pair, the elements of said second pair being disposed coaxial and coaxial with said first pair, the heating capacity of said second pair when connected to the phase electromotive force of said supply being approximately the same as the heating capacity of one of the elements of said first pair when connected to the phase electromotive force.

4. In combination: a plurality of electrical heating elements for connection to a multi-phase supply, the number of said heating elements being greater than the number of phases of the supply and being other than a multiple of said number of phases, said heating elements being so constructed and arranged that they are connectable to the supply to provide a balanced load on the supply.

5. In combination: a plurality of electrical heating elements in number other than a multiple of three, and said heating elements being relatively so constructed and arranged that they are connectable to a three phase source of supply to provide a balanced load on said supply.

6. In combination: housing means constructed and arranged to provide a passage for a stream of air; at least two electrical heating elements disposed in and transversely of said passage; said heating elements being so constructed and arranged that a first of said heating elements occupies a larger cross-sectional area of said passage than a second o f said heating elements; and said first heating element being constructed and arranged to dissipate a greater amount of heat than said second heating element.

'7. In combination: housing means constructed and arranged to provide a passage for a stream of air; at least two electrical heating elements disposed in and transversely of said passage, said heating elements each including a metallic sheath and a resistor disposed in and insulated from said sheath; said heating elements being so constructed and arranged that a first of said heating elements occupies a larger cross-sectional area of said passage than a second of said heating elements; and said first heating element being constructed and arranged to dissipate a greater amount of heat than said second heating element.

8. In combination: housing means constructed and arranged to provide a passage for a stream of air; a plurality of electrical heating elements for connection to a multi-phase supply, the number of said heating elements being greater than the number of phases of the supply and being other than a multiple of saidnumber of phases, said heating elements being disposed in and transversely of said passage and being so constructed and arranged that they are connectable to the supply to provide a balanced load thereon; said heating elements being so constructed and arranged that a first of said heating elements occupies a larger cross-sectional area of said passage than a second of said heating elements; and said first heating element being constructed and arranged to dissipate a greater amount of heat than said second heating element.

9. In combination: housing means constructed and arranged to provide a passage for a stream of air; a plurality of electrical heating elements for connection to a multi-phase supply, said heating elements each including a metallic sheath and a resistor disposed in and insulated from saidsheath, the number of said heating elements being greater than the number of phases of the supply and being other than a multiple of said number of phases, said heating elements being disposed in and transversely of said passage and being so constructed and arranged that they are connectable to the supply to provide a balanced load thereon; said heating elements being so constructed and arranged that a first of said heating elements occupies a larger crosssectional area of said passage than a second of said heating elements; and said first heating element being constructed and arranged to dissipate a greater amount of heat than said second heating element.

10. In combination: a plurality of electrical heating elements in number other than a multiple of three constructed andarranged for connection to a three phase source of supply to provide a.

balanced load on said supply, the number of said heating elements being at least four, a first two of which have substantially the same capacity and a second two of which each have one-half the capacity of either of the first two elements; and hous'mg means constructed and arranged to provide a passage for a stream of air, said heating elements being disposed in and transversely of said passage; and said heating elements being so constructed and arranged that said first two elements each occupya larger cross-sectional area. of said passage than each of said second two elements respectively.

11. In combination: housing means constructed and arranged to provide a passage for a stream of air; a plurality of electrical heating elements for connection to a multi-phase supply, constructed and arranged to provide a balanced load on said supply, the number of said heating elements being greater than the number of phases of the supply and being other than a multiple of said number of phases, at least two of said heating elements each having a capacity a predeter- I mined fraction of the individual capacity of others of said elements; means for so connecting said elements to the supply that the load on the supply is balanced; and said heating elements being disposed in and transversely of said passage and being so constructed and arranged that each of said at least two heating elements occupies a smaller cross-sectional area of said passage than others or said heating elements.

12. In combination: housing means constructed and arranged to provide a passage for a stream of air; a plurality of electrical heating elements for connection to a multi-phase supply, constructed and arranged to provide a balanced load on said supply, the number of said heating elements being greater than the number of phases of the supply and being other than a multiple of said number of phases, at least two of said heating elements each having a capacity a predetermined fraction of the individual capacity of others of said elements; means for so connecting said elements to the supply that the load on the supply is balanced; said heating elements being disposed in and transversely of said passage and being so constructed and arranged that they are arcuate and coaxial and that each of said at least two heating elements occupies a smaller cross-sectional area of said passage than others of said heating elements.

13. In combination: a plurality of electrical heating elements, for connection to a three-phase supply, constructed and arranged to provide a balanced load on said supply, the number of said heating elements being at least four and being other than a multiple of three, a first two of a group of four of said heating elements each having substantially the same heating capacity when supplied with a given electromotive force, and a second two of said group of heating elements each having approximately one-half of the heating capacity of one of said first two heating elements when supplied with said given electromotive force; and means for so connecting said group of elements to the supply that the load on the supply is balanced.

14. In combination: housing-means constructed did arranged to provide a passage for a stream of air; a plurality of electrical heating elements, for connection to a three-phase supply,

' constructed and arranged to provide a balanced load on said supply, the number of said heating elements being at least four and being other than amultiple of three, a first two of a group of four of said heating elements each having substantially the same heating capacity when supplied with a given electromotive force, and a second two of said group of heating elements each having approximately one-half of the heating capacity of one of said first two heating elements when supplied with said given electromotive force; means for so connecting said group of elements to the supply that the load on the supply is balanced; and said heating elements being disposed in and transversely of said passage and being so constructed and arranged that said first two of said heating elements occupy approximately equal cross-sectional areas of said passage and said second twoof said heating elements occupy approximately equal cross-sectional areas of said passage, said last-named cross-sectional areas being smaller than said first-named cross-sectional areas.

15. In combination: housing means constructs ed and arranged to provide a passage for a stream of air; a plurality of electrical heating elements, for connection to a three-phase supply, constructed and arranged to provide a balanced load on said supply, the number of said heating elements being at' least four and being other than a multiple of three, a first two of a group of four of said heating elements each having substantially the same heating capacity when supplied with a given electromotive force, and a second two of said group of heating elements each having approximately one-half of the heating capacity of one of said first two heating elements when supplied with said given electromotive force; means for so connecting said group oif elements to the supply that the load on the supply is balanced; and said heating elements being disposed in and transversely of said passage and being so constructed and arrangedthat said first two of said heating elements are arcuate and occupy approximately equal cross-sectional areas of said passage and define coaxial circles, and said second two of said heating elements are arcuate and occupy approximately equal crosssectional areas of said passage and define smaller circles coaxial with said first-named circles so that said last-named cross-sectional areas are smaller than said first-named cross-sectional;

areas.

ERNEST N. CALHOUN. 

